1. Field of the Invention
The invention relates to the field of phase-resolved functional optical coherence tomography systems and in particular to systems which can obtain the Stokes vectors, structure, blood flow velocity, standard deviation, and birefringence images in tissue.
2. Description of the Prior Art
Optical coherence tomography (OCT) is a noninvasive, noncontact imaging modality that uses coherent gating to obtain high-resolution cross-sectional images of tissue microstructure. OCT is analogous to ultrasound imaging except that infrared light waves rather than acoustic waves are used. Consequently, the spatial! resolution of OCT is more than an order of magnitude better than that of the ultrasound. OCT was first used clinically in ophthalmology for the imaging and diagnosis of retinal disease. Recently, OCT has been applied to imaging subsurface structure in human skin, blood vessels, oral cavity and the respiratory, urogenital, and GI tracts.
Several extensions of OCT have been developed for functional imaging of tissue physiology. For example, optical Doppler tomography (ODT) combines the Doppler principle with coherence gating for tomographic imaging of tissue microstructure and blood flow simultaneously. See Nelson, et al., “Method And Apparatus For Optical Doppler Tomographic Imaging Of Fluid Flow Velocity In Highly Scattering Media,” U.S. Pat. No. 5,991,697 (1999), which is incorporated herein by reference. Polarization sensitive OCT (PS-OCT) combines polarization sensitive detection with OCT to determine tissue birefringence. See De Boer, et al., “Birefringence Imaging In Biological Tissue Using Polarization Sensitive Optical Coherent Tomography,” U.S. Pat. No. 6,208,415 (2001), which is incorporated herein by reference. Both techniques use the phase information from the interference fringes to obtain additional physiologically important information. Although a number of potential clinical applications of ODT and PS-OCT have been demonstrated, to date, ODT and PS-OCT imaging have been performed using separate systems. However, there are many clinical indications where determination of both blood perfusion and tissue birefringence is important. For example, in burn injuries both the loss of cutaneous blood perfusion and changes in tissue birefringence are two critical factors used to determine burn depth. Simultaneous imaging of the changes in blood perfusion and collagen birefringence by functional OCT (F-OCT) will according to the invention allow better clinical management of burn injuries.